+ Wood is sustainable, strong, attractive, and can be surprisingly resistant to fire. Photo credit and copyright: Blumer Lehmann.

I don’t know about you, but I’d be perfectly happy to live in a 20-storey wooden building. Wood is sustainable, strong, attractive, and can be surprisingly resistant to fire.

With urbanisation driving cities to build densely and sustainably, I think using wood in tall buildings is an appealing option. For one thing, it’s the only completely renewable building material. Second, wood has almost zero embodied energy because it’s grown with solar power.

It’s also a cellular material like bone, so it’s strong and light. Relatively easy to work with, wood lends itself to high quality prefabrication techniques. It’s light to transport to site, reducing transport costs and carbon emissions. And it’s light to lift into place, reducing the size of cranes required and making the process safer.

What about the fire risk? The massive timber construction necessary for taller buildings doesn’t burn readily, even without protection. Just like a log on a fire, a large timber beam may char on the surface but will still retain its integrity for hours. Compare that to how a steel beam would behave in a fire. Without lots of protection, it would quickly sag and lose its stiffness.

Unfortunately, building codes around the world often dictate that the structure of a building should be non-combustible. This completely precludes timber. There are other codes that require the timber to be protected by plasterboard. I believe that’s too simplistic. What really matters is that people can escape safely, that the fire brigade isn't put at risk and that the fire doesn’t spread to other buildings.

We need to address this issue if we are to create successful wooden buildings. This means we need to start assessing wooden buildings in a proper “fire engineering” way exactly as we do for steel buildings. In other words we need to look at how the overall building behaves rather than just looking at the charring of individual wooden elements. The nine-storey wooden Stadthaus development in London was a great achievement, but it’s a tragedy that the wood is completely hidden behind protective plasterboard. I want to engineer safe buildings and also still see the beauty of the wood.

Stadthaus, and the slightly taller Forte tower in Melbourne, were firsts. So it was right that they should adopt relatively simple structural solutions with regular timber walls. But if we really want to develop sustainable buildings that are going to last, then I feel they need columns rather than solid structural walls. This would enable them to adapt in the future to suit changing needs and to be used for open-plan offices.

It’s clear that wood has potential for use in tall buildings. Technically, I think we could build 40 storeys in wood if we wanted to. But we also have a duty to come up with economic solutions, and I think that is where using wood in combination with other materials is an intelligent option.

For one thing, there aren’t enough trees for us to build everything out of 100% wood. And anyway, wood, steel and concrete all have particular advantages that we should be looking to exploit. All I’m arguing is that we should be starting to look at wood as a standard option alongside steel and concrete to see if it’s right for a particular building.

On taller buildings I expect we’ll start to see wood used in conjunction with other materials. For example, we could see timber columns and floors with a concrete core to provide lateral stability. By making the most of the advantages of wood in combination with other materials, we can create buildings in which anyone would be pleased to live.

Amendments

Added 15 October 2013: This means we need to start assessing wooden buildings in a proper “fire engineering” way exactly as we do for steel buildings. In other words we need to look at how the overall building behaves rather than just looking at the charring of individual wooden elements.

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Comments /

Vishaal

Hi, I have just been to India where we saw some palaces and buildings constructed completely out of Teak wood. Very beautiful looking.

The risk is still fire, termites and water which can destroy wood and therefore its integrity. Will the steel sag much quicker than the wood would burn. Its all questions that arise when think about wood construction.

I think it is a good idea to investigate further though. Engineers have constantly improved structures by optimizing designs to meet requirements. A simple I-beam uses the strength of steel while its cross section optimized to only use necessary amount of steel to reduce weight. Re-enforced concrete uses the compressive strength of concrete mixed with the toughness of steel.

I don't see why wood cannot be utilized in the best possible manner in combination with other materials. In USA you seen many of the houses being built out of wood. Another problem is that despite wood being sustainable and renewable material, trees will still have to be cut and whether this happens at a faster rate than it is being used is a potential flaw that good lead to a good idea going in the wrong direction.

A good topic to investigate and look into for future development though...

Tristram Carfrae

I absolutely agree with you that timber should be a "standard" material to be considered alongside and together with steel and concrete.

How do we educate architects and engineers and provide them with sufficient knowledge to feel comfortable in designing with wood? We all need to understand the issues, in detail, before we will become comfortable - so the more discussion the better!

Peter Bressington

I agree and totally see where you are coming from, but it should be made clear that you are talking about structural elements. Other timber in the construction will need some form of fire protection, this is an issue for timber buildings in construction where there have been a number of high profile building site fires.

Johan Karlsson

Great article. Not only do we reduce carbon dioxide by using trees in construction (since it's contained in the material) but we double that effort when planting new trees. That's pretty much exactly the opposite to materials such as concrete, releasing almost two tonnes of carbon dioxide equivalent for every tonne of material produced. Needless to say, we have a great opportunity to offset and reduce emissions associated with construction by using wood.

Carl Maletic, Architect

In 1989 I was working in San Francisco for a premier structural engineering firm. When the Loma Prieta 7.1 earthquake hit the Bay Area at 5:04 p.m. I was in my office, and the building literally did a "rock & roll" gyration . . . moving a minimum of 3-ft. laterally in two directions.

I escaped via the exit stair from my third story office; but the good news is that our building resisted this major, devastating seismic event exceptionally well, with no damage. Why? Number One: we designed the building. Number Two: we designed it with heavy wood timber.

As an architect and structural engineer. Wood is flexible, and it moves with the quake. Rather than trying to resist the ground motion; it's lateral acceleration matches, and flows with the quake. I have no problem with designing mid-size high rises with timber construction.

The new building ordinances in places like Seattle and elsewhere are a welcome realization that wood structure structures perform very well during seismic events.

Maximilian Keatinge

John White

Armin Wolski

Eloquent yet succinct! Thank you Andrew. Be on the lookout for the U.S. based National Fire Protection Research Foundation Project on tall timber buildings. The first phase, a literature search and gap analysis is underway, performed and supported by Arup.

Richard Matthews

Andrew, a very good article. I have long liked the idea of timber buildings. I think the opportunity is there, our challenge is in being clear about the benefits, organising the supply chain and ensuring the regulatory and insurance industries keep up with us.

Over the years I have seen a number of really good well thought through building systems fail to take off because the complete end to end story had not been thought through and addressed.

So from a client's point of view, what is the benefit? Why take the risk of trying something new? We need to articulate this very clearly.

From the designers point of view, do we all know how to design and detail in timber cost effectively. Do the follow-on trades and fit out designers know how to interface with our new design and detail around it? My experience of new systems that have been half thought through is that they solve a primary problem really well but inadvertently create a new expensive problem for a follow-on trade.

From the contracting supply chain point of view, does the supply chain have plenty of capacity and are there several equally competent suppliers in the market? Having 3 or more tenderers to go to is a key part of convincing the client that his design isn't tied to one supplier. That has been the downfall of a number of very neat system build ideas, they were developed and marketed by just one firm. No competition.

And finally, can we get Building Authority approval for the design and can the client insure and maintain his building in the future?

If we have all these pieces in place I think we could have a very successful timber frame business.

Andy Gardner

A great article, and equally fantastic building photographed: almost the timber equivalent of the Pompidou or Llyods buildings. Is the timber exposed?

Building on Richard Matthews' comment and in addition to what he says, I think mass up-take of timber would need buy-in of software companies to develop sophisticated design packages for timber equivalent to those for steel and concrete. In part it pains me to say this because software lead design shouldn't rule the roost. But it's a reality of engineering that software is becoming more critical to the delivery of work on time and to budget.

Software development is of course a little chicken and egg. Steel and concrete were widely used before computers and software developed to catch up; there is no precedent for something becoming established in the reverse.

E Halford

Congratulations on your splendid achievement. How do the economics compare with more conventional construction materials? This project is clearly a 'prestige' building.I am also a structural engineer, though FICE, and would have been proud to have worked on a project of this nature. I thoroughly agree with your comments relating to timber construction.

Rory Martin

I absolutely agree. I worked for Feilden Clegg Bradley Studios & Ramboll on a Cross Laminated Timber school in North Ealing in London. This construction method suprised even Kier Construction for its elegance during the construction phase.We did have to work extremely hard to expose the timber in specific areas, andfor the majority of the building the timber was hidden by multiple layers of gypsum board. Unfortunately the CLT supplier/ subcontractor had not carried out formal fire or acoustic tests in the UK for this method of construction, with or without treatments or finishes. The end result is a seriously over engineered building from a lining point of view! Both fire engineering & acoustic engineers have some work to do with the suppliers of this type of material & BRE before it can become more widely used.All being said, the end result was a very elegant building.

John Brunette

Rory, I'm keen to more more about your experience with the restrictions placed on CLT and the over engineering of the end product. I’m a student studying my final year of Construction Management at the University of Newcastle in Australia and currently researching for my thesis on this subject and your point struck a chord.

My thesis topic is focused on whether current acceptance of timber in high rise construction by various international construction bodies/building codes is reflective of its structural and fire performance characteristics. Despite recent changes to many codes there doesn’t seem to be consistency among policy makers, some codes are starting to embrace timber while other still reject or heavily restrict it.

If you can share any information with me it would be greatly appreciated.

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